Plenum chamber for discharging gas jets against strip material



Sep 1965 J. A. SCHARBROUGH 3,206,370

PLENUM CHAMBER FOR DISCHARGING GAS JETS AGAINST STRIP MATERIAL Filed Jan. 2, 1962 2 Sheets-Sheet l & PRIOR ART 5 FIG.)

fimlllllll l lllllllll INVEN TOR. JAMES A. SCHARBROUGHI ATTORN EV Sept. 21, 1965 J. A. SCHARBROUGH 3,206,870

PLENUM CHAMBER FOR DISCHARGING' GAS JETS AGAINST STRIP MATERIAL Filed Jan. 2, 1962 2 Sheets-Sheet 2 INVENTOR. JAMES A. SCHARBROLLGH ATTORNEY United States Patent 3,206,870 PLENUM CHAMBER FOR DlSCI-IARGIN G GAS JETS AGAINST STRIP MATERIAL James A. Scharbrough, Boggstown, Ind, assignor to General Electric Company, a corporation of New York Filed Jan. 2, 1962, Ser. No. 163,479 9 Claims. (Cl. 34-155) The present invention relates to gas discharge units for the thermal treatment of continuously moving strip of metal or the like and more particularly to an improved plenum chamber construction for such discharge units.

Gas discharge units for the thermal treatment of metal in strip form have in the past utilized jets of gas issuing from suitably positioned orifices in a wall of a plenum chamber of a high velocity jet discharge unit toward the strip which moves in a plane substantially parallel to and adjacent to the Wall of the plenum chamber having the orifices. When the velocities of the various jets of gas are unsymmetrically balanced with respect to the center line of the strip path, or when the jets impinge upon the moving strip at varying unsymmetrical angles of incidence, strip flutter or twist may result. Strip flutter or twist of the moving material may cause the strip to physically engage the gas discharge units and result in damage to the strip. To avoid strip flutter or twist and to provide optimum thermal treatment of the strip material, the discharge jets of gas should be substantially symmetrically balanced transversely of the strip and preferably should be discharged substantially at right angles to the plane of the strip path. These conditions can be realized in the momentum of the gas as it enters the plenum chamber is dissipated so that it does. not afiect the velocity or direction of the gas issuing from each of the orifices.

Presently known gas discharge units do not provide these optimum conditions. These gas discharge units have plenum chamber constructions that donot compensate for the inherent momentum of an entering gas flow to the chamber. The momentum of the gas has a tendency to continue to move the gas in the direction in which it enters the chamber and thereby affect the velocity and direction of the gas jets issuing from the various orifices of the plenum chamber so that they are both unbalanced and directed at something other than right angles to the plane of the plenum chamber wall. The unbalanced or unsymmetrical gas pressures and the various unsymmetrical angles of incidence are believed to result in the development of undesirable strip flutter and twist and the inefficient thermal treatment of the strip material.

Accordingly, it is an object of the present invention to provide a new and improved plenum chamber construction for gas discharge units.

Another object of the present invention is to provide a new and improved plenum chamber construction for developing substantially symmetrical angles of discharge of a gas from the plenum chamber.

A further object of the present invention is to provide a new and improved plenum chamber construction for the discharge of a gas in the form of jets from the plenum chamber at substantially uniform velocities and symmetrically balanced directions.

Another object of this invention is to provide an improved plenum chamber for discharging jets of gas across the path of movement of moving strip material in a manner whereby the jets of gas impinge across the strip with symmetrically balanced pressures and angles.

Briefly, in accordance with one form of the present invention, a gas discharge unit is provided for discharging jets of gas against and across the path of strip movement of an adjacent moving strip of material comprising a plenum chamber having a pair of discharge walls with 3,206,870 Patented Sept. 21, 1965 orifice means in said walls. The plenum chamber is adapted to be positioned with the walls having the discharge orifice means being parallel to and across the path of movement of the strip. A duct insert for delivering gas to the plenum chamber is positioned within the plenum chamber and is provided with an egress means which is substantially centered along the center line of the orifice means of the plenum chamber and constructed so as to substantially dissipate the momentum of the gas coming into the plenum chamber which causes the gas in the plenum chamber to move transversely of the strip path. Preferably the egress means of the duct insert is positioned in a wall that is oriented generally perpendicular to the discharge walls of the plenum chamber.

The organization and operation together with further objects and advantages of the invention may best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a fragmentary schematic view showing the gas discharge flow from a prior art form of plenum chamber against an adjacent moving strip of material;

FIG. 2 is a perspective view partly broken away of a gas discharge unit having a new and improved plenum chamber construction formed in accordance with the present invention;

FIG. 3 is a perspective view of a duct insert or internal conduit for the new and improved plenum chamber shown in FIG. 2;

FIG. 4 is a fragmentary schematic view showing optimum gas discharge flow realized from the new and improved plenum chamber construction formed in accordance with the present invention; and

FIG. 5 is a perspective view on a slightly reduced scale of a modified form of a duct insert or internal conduit for use in the plenum chamber.

Referring now to FIG. 1, there is shown a fragmentary schematic view of a prior art form of plenum chamber which receives an entering gas flow from one end thereof, as indicated by the flow arrows from a suitable source of gas under pressure. The plenum chamber 1 has a pair of discharge walls 2 which are shown as being provided with a plurality of transversely spaced orifices 3 and is positioned so that the gas discharged through the orifices 3 will engage strip 4 that is to be thermally treated. As shown in FIG. 1, the moving strip 4 is moving in a strip path in the direction either into or out of the drawing. A suitable housing 5 is shown schematically to complete one form of structural arrangement that is generally required for the thermal treatment of the strip metal 4.

The high velocity jets of gas exhausting from the orifices 3 impinge upon and etfectively penetrate a boundary layer of air which is carried by the moving strip 4 due to its relatively high speed of travel along the strip path. To minimize strip flutter or twist, the discharge flow should be substantially perpendicular to the walls 2 and the velocities of the gas jets being discharged from the orifices 3 should be symmetrically balanced across the path of strip movement. However, when the new and improved plenum chamber construction of the present invention is not utilized, the actual unbalanced gas discharge flow from the plenum chamber 1 is shown by the dashed flow arrows in FIG. 1.' The entering gas flow to the plenum chamber 1 has an inherent momentum which tends to continue to move the gas in generally the same direction as the entering gas flow. Thus, it is believed that the jets of gas discharging from. the orifices 3 in the walls 2 leave the plenum chamber 1 at angles of incidence other than generally symmetrically, or at right angles, to the discharge wall 2 in the view shown in FIG. 1. The unbalanced gas discharge flow and the impingement by the jets of gas at undesired angles of incidence to the adjacent moving strip 4 are believed to be the cause of strip flutter or twist.

Turning now to FIG. 2 there is shown one form of gas discharge unit embodying the new and improved plenum chamber construction of the invention. The gas discharge unit 10 illustrates one type of unit which is suitable for use in the thermal treatment of a moving strip of metal that passes adjacent to a discharge wall 11 of the gas discharge unit 10. In the usual construction the wall 11a opposite to discharge wall 11 is also a discharge wall past which the moving strip travels during its thermal treatment.

The internal construction of a gas discharge unit 10 in the form shown by FIG. 2 comprises a plurality of contiguous compartments with a suitable ingress and egress gas flow permitted through the discharge unit 1Q, as indicated by the flow arrows in FIG. 2. The discharge walls 11 and 11a of the gas discharge unit 10 have a plurality of suitably positioned orifices 12 to permit egress of the gas flow from the discharge unit 10 to and across a material or metal not shown, which is thermally treated when positioned adjacent to the walls 11 and 11a. As better shown in FIG. 4, these orifices extend laterally of, and are centered with respect to, the strip path. A wall 15 of the gas discharge unit 10 has an intermediate opening or window 16 while an oppositely disposed wall 17 of the gas discharge unit 10 has a similar intermediate opening or window 18. The windows 16 and 18 permit the ingress into the gas discharge unit 10 of the gas discharged from orifices 12 for recirculation therethrough.

A longitudinally extending compartment 20 receives the gas entering the gas discharge unit 10 through the window 16. Similarly, an oppositely disposed compartment 21 extends longitudinally and receives the gas entering the gas discharge unit 10 through the Window 18. The gas is drawn from the compartments 20 and 21 into a blower compartment 22 by means of a fan or blower 23 that is mounted within a suitable fan or blower casing 24. The casing 24 has an inlet aperture 25 that communicates with the blower compartment 22 to permit the gas being drawn from the outer compartments 20 and 21 to enter and pass through the fan or blower casing 24. An inner compartment 28 receives the high pressure output gas from fan 23. Although a fan or blower 23 is shown by FIG. 2, a source of gas under pressure that would induce gas flow through the gas discharge unit 10 is considered to be within the concept of the present invention.

In accordance with this invention, means are provided for dissipating the momentum of the gas entering plenum chamber 1. As shown in FIG. 2, a duct insert or internal conduit 30 is provided to perform this function. Duct insert or internal conduit 30 is positioned within and spaced from the inner compartment 28 to form the new and improved double wall plenum chamber construction for the gas discharge unit 10. The duct insert or internal conduit 30 is shown in FIG. 3 as having an end Wall 31 with a suitable aperture 32 therein that permits the entering gas flow from the fan or blower casing 24 to pass into the duct insert 30. The end wall 31 of the duct insert 30 provides a gas seal within the compartment 28 to cause the longitudinal flow of the entering gas from the casing 24 to pass into the duct insert 30 through the aperture 32. The end wall 31 prevents gas flow from the casing 24 from entering the external space that surrounds the duct insert 30 between the walls of duct insert 30 and the inner compartment 28. Oppositely disposed walls 33 and 34 of the duct insert 30 in conjunction with oppositely disposed walls 37 and 38 develop the box-like duct insert 30. The Walls 33 and 34 are sealed to the end wall of the plenum chamber 10 and are preferably imperforate. Wall 37 of the duct insert 30 has an intermediate aperture or window 39 positioned generally opposite a similar intermediate aperture or window 40 in the oppositely disposed wall 38. The duct insert or internal conduit 30 is longitudinally so positioned within the inner compartment 28 of the gas discharge unit 10 that the windows 39 and 40 are positioned substantially on the transverse centerline of the orifices 12 of the discharge walls 11 and 11a, and a double-box plenum chamber construction is thus provided. The gas flow, indicated by the flow arrows in FIG. 2, passes through the aperture 32 of the end wall 31 and enters the box-like duct insert 30. The momentum of the output gas from fan 23 i dissipated since the gas cannot flow directly from port 32 to the orifices 12. Rather, the walls 33 and 34 serve as baflies to dissipate the momentum of the gas within plenum chamber 10 in a radial direction from the fan 23 by causing the air to change its direction of flow as indicated by the arrows of FIGS. 2 and 4, so that it flows substantially perpendicular with respect to its direction in entering the plenum chamber through port 32. It will be apparent that momentum of gas as it leaves duct insert 30 will have little effect on the angle at which the gas is discharged through the orifices 12 in the plane shown in FIG. 4 of the drawing. In this connection, with the windows 39 and 40 substantially positioned on the centerline of the orifice means 12, any lateral flow of the gas from windows 39 and 40 at an angle with respect to the centerline of the plane shown in FIG. 4 would be symmetrical with respect to the centerline and forces on the strip 4 at other than right angles would be balanced. Thus it can be seen that the flow of gas from the opposed windows 39 and 40 enters the space between the duct insert 30 and the inner compartment 28 to discharge from the orifices 12 in a pattern which is symmetrically balanced and substantially parallel to a plane perpendicular to the discharge wall 11 and through the transverse centerline of the orifices 12.

FIG. 4 shows the substantially optimum symmetrical discharge pattern of the gas from orifices 12 which is essentially realized by the new and improved plenum chamber construction of the invention. The gas discharge unit 10, previously described and shown by FIG. 2 with the duct insert or internal conduit 30, is positioned with the discharge walls 11 and 11a generally over and adjacent to a strip path that is defined by a moving strip of material or metal 4 which moves in a plane parallel to and spaced from the discharge walls 11 and 11a. The strip 4 is shown by FIG. 4 to be moving into or out of the drawing and is substantially centered on the transverse centerline of the orifice means 12 of discharge Walls 11 and 11a so that the discharge of gas through the orifices 12 of the discharge walls 11 and 11a are generally across the path of movement of the strip 4. An entering longitudinal gas flow into the plenum chamber from a suitable source of gas under pressure passes through the aperture 32 in the end wall 31 of the duct insert 30. The entering longitudinal gas fiow is discharged or released from the duct insert 30 through the intermediate windows 39 and 40 so that the discharge is centered substantially on the transverse centerline of the orifices 12. It is contemplated, as previously described and shown by FIG. 3, that oppositely disposed windows or a plurality of suitable intermediate apertures or windows in the duct insert 30 are within the concept of the present invention when such apertures are interinediately positioned so as to result in a gas discharge to the input of the orifices 12 that is substantially centered on the transverse centerline of the orifices 12 and substantially perpendicular to the gas flow entering the plenum chamber 10 from fan 23. The exhaust flow from the boxlike duct insert 30 to the inner compartment 28 is generally perpendicular to the entering longitudinal gas flow. The duct insert 30 thus serves as an internal bafile means in the plenum chamber of the gas discharge unit 10 to cause an entering gas flow to change directions and subsequently exhaust through the orifices 12 in the discharge wall 11 in a direction that is substantially perpendicular to the discharge wall 11 and with symmetrically balanced pressures across the strip path of movement of the strip 4. The jets of gas will impinge at substantially right angles to an adjacent moving strip 4 when the strip path, as previously discussed, is parallel to and spaced from the discharge wall 11. This substantially right angle impingement of the strip 4 by the jets of gas achieves the desired optimum penetration of the boundary layer that is, carried by the moving strip 4 so that efficient thermal treatment of the strip material is realized. The duct insert 30 in the new and improved plenum chamber construction with the opposed windows 39 and 40 substantially centered over the center line of the moving strip 4 symmetrically balances the discharge gas pressure of the jets that issue through the orifices 12 in a direction that is substantially perpendicular to the discharge wall 11 and in the general direction of strip movement. The symmetrical pressure balance and symmetrical orientation of the issuing jets effectively reduces pressure unbalances on the strip to minimize strip flutter or twist.

Turning now to FIG. 5, there is shown a modified form of the insert duct 30 for use in the plenum chamber of FIG. 2. This modification involves a pair of plates 133 and 134 having edges which are sealed with respect to the interior surfaces of the plenum chamber 10. Intermediate openings 139 and 140 provide for the flow of gas from between the plates to the space between these plates and walls 11 and 11a containing orifice means 12. In flowing through openings 139 and 140', the direction of flow is substantially perpendicular to its direction as it enters through port 32. Thus it will dissipate the effects of the momentum of the entering gas and provide substantially symmetrical balanced flow of gas from orifices 12.

As it will be evidenced from the foregoing description, certain aspects of the invention are not limited to the particular details of construction illustrated. It is therefore contemplated that other modifications of the new and improved plenum chamber construction will occur to those skilled in the art. Therefore, it is intended that the appended claims shall cover such modifications that do not depart from the true spirit and scope of the invention.

Having described the invention, what is claimed is:

1. A gas discharge unit for discharging jets of gas against and generally across the path of movement of an adjacent moving strip of material comprising,

(a) a plenum chamber having at least a portion thereof having a discharge wall with a plurality of orifices in said wall,

(b) said chamber adapted to be positioned with said discharge wall extending generally across the path of movement of the strip material to be treated and with a pair of walls, adjoining said discharge wall, each wall formed with an inlet opening to provide for ingress of air to said plenum chamber;

(c) an inner and an outer compartment means within said plenum chamber, said inlet openings communicating with said outer compartment means;

(d) a duct insert having an imperforate wall;

(e) said insert being positioned within said inner compartment with said imperforate wall generally parallel to said discharge wall and spaced from said discharge Wall; said discharge wall forming a Wall of said inner compartment;

(f) a gas ingress means in said insert for the admission of gas under pressure; and

(g) at least one window in said insert at a point intermediate said discharge wall and positioned symmetrically with respect to the transverse centerline of the orifices in said discharge wall whereby gas discharge flow from said window into said chamber is constrained to discharge generally symmetrically through said orifices of said discharge wall.

2. A gas discharge unit for discharging jets of gas 6 against and generally across the path of movement of an adjacent moving strip of material comprising,

(a) a plenum chamber having a discharge wall with at least a portion thereof having a plurality of orifices;

(b) said chamber being adapted to be positioned with said discharge wall and extending generally across the path of movement of the strip material to be treated;

(c) an inner an outer compartment formed within said plenum chamber, said outer compartment communicating with said inlet opening and said portion of said discharge Wall forming one wall of said inner compartment;

((1) a duct insert having an imperforate wall;

(e) said insert being positioned within said inner compartment with said imperforate w-all generally parallel to said discharge wall, said imperforate wall being spaced from the discharge wall of said plenum chamber;

(f) a gas ingress means in said insert for the admission of gas under pressure; and

(g) at least one window disposed in a wall of said insert extending essentially perpendicular to the discharge wall and located at a point intermediate said discharge wall and positioned symmetrically with respect to the transverse center line of said orifices formed in said discharge wall whereby gas discharge flow from said window into said chamber is constrained'to discharge generally symmetrically through said orifices of said discharge wall.

3, The gas discharge unit of claim 2 in which said duct insert has a pair of generally opposed windows to constrain said gas discharge flow from the windows.

4. A gas discharge unit for discharging jets of gas against and generally across the path of movement of an adjacent moving strip of material comprising,

(a) aplenum chamber having a discharge wall having a portion formed with a plurality of orifices and having an inlet opening formed near said portion of the discharge wall;

(b) said chamber being adapted to be positioned With said discharge wall extending generally across the path of movement of the strip material to be treated;

(c) an outer compartment means and an inner compartment, said portion of said plenum chamber with said orifices forming a wall of said inner compartment;

(d) a box-like duct insert having top, bottom, side and end walls;

(e) said insert being positioned in said. inner compartment with a bottom wall parallel to said discharge wall and spaced therefrom;

(f) an inlet opening in an end wall of said insert for the admission of gas under pressure; and

g) an outlet opening in a side wall of said insert at a point intermediate said discharge wall and positioned symmetrically with respect to the transverse center line of said orifices whereby gas discharge flow from said inlet opening through said outlet opening is constrained to discharge generally symmetrically through said orifice of said discharge wall.

5. A gas discharge unit of claim 4 in which said duct insert has a pair of generally opposed outlet openings to constrain said gas discharge flow from said outlet openings.

6. A gas discharge unit for discharging jets of gas against and generally across the path of movement of an adjacent moving strip of material comprising,

(a) an outer casing having a discharge wall with an orifice portion thereof formed with a plurality of orifices;

(b) a pair of outer compartments in said casing including a first compartment and a second compartment separated from said first compartment with an inner compartment in said casing therebetween;

(c) said orifice portion of said discharge wall of said casing forming a wall of said inner compartment;

(d) said outer casing being adapted to be positioned with said discharge wall extending generally across the path of movement of the strip material to be treated;

(e) a blower means in said outer casing;

(f) gas egress means from said pair of outer compartments to said blower means;

(g) a duct insert having an imperforate wall;

(h) said duct insert being positioned within said inner compartment and spaced from the interior Walls of the inner compartment with said imperforate wall generally parallel to said discharge wall and spaced therefrom;

(i) a gas ingress means in said insert for the admission of gas under pressure from said blower means; and

(j) at least one window in said insert at a point intermediate said discharge wall and positioned sym metrically with respect to the transverse centerline of said orifices whereby gas egress from said window into said inner compartment is constrained to egress generally symmetrically through said orifices of said discharge wall.

7. The gas discharge unit of claim 6 in which said duct insert has a pair of generally opposed Windows to constrain said gas egress from the windows.

8. A gas discharge unit for discharging jets of gas against and generally across the path of movement of an adjacent moving strip of material comprising,

(a) an outer casing having a discharge wall with an orifice portion thereof formed with a plurality of orifices and having adjoining walls formed with an inlet opening;

(b) a pair of outer compartments in said casing including a first compartment and a second compartment separated from said first compartment with an inner compartment in said casing therebetween said first and second compartments respectively communicating with the inlet openings;

(c) said orifice portion of said discharge wall of said casing forming a wall of said inner compartment; (d) said outer casing being adapted to be positioned with said discharge wall extending generally across the path of movement of the strip material to be treated;

(e) a blower means in said outer casing for drawing air from said first and second compartments and supplying air under pressure to said inner compartment;

(f) gas egress means from each of said pair of outer compartments to said blower means;

(g) a box-like duct insert having top, bottom, side and end walls;

(h) said insert being positioned in said inner compartment with a bottom wall parallel to said discharge wall;

(i) a gas ingress means in an end wall of said insert for the admission of gas under pressure from said blower means; and

(j an outlet opening in a side wall of said insert at a point intermediate said discharge wall whereby gas discharge flow from said inlet opening through said outlet opening is constrained to discharge generally symmetrically through said orifice of said discharge wall.

9. The gas discharge unit of claim 8 in which said duct insert has a pair of generally opposed outlet openings to constrain said gas discharge flow from said openings.

References Cited by the Examiner UNITED STATES PATENTS 1,914,024 6/33 Kasanof 34155 1,951,004 3/34 Willis 34-156 2,133,330 10/38 Oifen 34-156 2,391,764 12/45 Andrews 34-l56 2,602,314 7/52 Cohn 34l60 2,671,279 3/54 Blanchard 34159 2,848,820 8/58 Wallin et al. M 34156 3,068,586 12/62 Vaughan et al. 34159 3,102,009 8/63 Blonn 34-159 3,134,654 5/64 Russell 34160 FOREIGN PATENTS 668,741 3/52 Great Britain.

WILLIAM F. ODEA, Acting Primary Examiner.

NORMAN YUDKOFF, Examiner. 

1. A GAS DISCHARGE UNIT FOR DISCHARGING JETS OF GAS AGAINST AND GENERALLY ACROSS THE PATH OF MOVEMENT OF AN ADJACENT MOVING STRIP OF MATERIAL COMPRISING. (A) A PLENUM CHAMBER HAVING AT LEAST A PORTION THEREOF HAVING A DISCHARGE WALL WITH A PLURALITY OF ORIFICES IN SAID WALL. (B) SAID CHAMBER ADAPTED TO BE POSITIONED WITH SAID DISCHARGE WALL EXTENDING GENERALLY ACROSS THE PATH OF MOVEMENT OF THE STRIP MATERIAL TO BE TREATED AND WITH A PAIR OF WALLS, ADJOINING SAID DISCHARGE WALL, EACH WALL FORMED WITH AN INLET OPENING TO PROVIDE FOR INGRESS OF AIR TO SAID PLENUM CHAMBER; (C) AN INNER AND AN OUTER COMPARTMENT MEANS WITHIN SAID PLENUM CHAMBER, SAID INLET OPENINGS COMMUNICATING WITH SAID OUTER COMPARTMENT MEANS; (D) A DUCT INSERT HAVING AN IMPERFORATE WALL; (E) SAID INSERT BEING POSITIONED WITHIN SAID INNER COMPARTMENT WITH SAID IMPERFORATE WALL GENERALLY PARALLEL TO SAID DISCHARGE WALL AND SPACED FROM SAID DISCHARGE WALL; SAID DISCHARGE WALL FORMING A WALL OF SAID INNER COMPARTMENT; (F) A GAS INGRESS MEANS IN SAID INSERT FOR THE ADMISSION OF GAS UNDER PRESSURE; AND (G) AT LEAST ONE SINDOW IN SAID INSERT AT A POINT INTERMEDIATE SAID DISCHARGE WALL AND POSITIONED SYMMATRICALY WITH RESPECT TO THE TRANSVERSE CENTERLINE OF THE ORIFICES IN SAID DISCHARGE WALL WHEREBY GAS DISCHARGE FLOW FROM SAID WINDOW INTO SAID CHAMBER IS CONSTRAINED TO DISCHARGE GENERALY SYMMETRICALLY THROUGH SAID ORIFICES OF SAID DISCHARGE WALL. 